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Using FEHT. Keith A. Woodbury. Introduction. FEHT Is a simple finite element conduction heat transfer analysis program Use of this program entails the same basic steps necessary to solve heat transfer problems with commercial software Is restricted to 2-D problems with less than 1000 nodes
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Using FEHT Keith A. Woodbury
Introduction • FEHT • Is a simple finite element conduction heat transfer analysis program • Use of this program entails the same basic steps necessary to solve heat transfer problems with commercial software • Is restricted to 2-D problems with less than 1000 nodes • Can solve steady or unsteady (transient) problems
Overview • Numerical heat transfer analysis requires the following steps • Define geometry • Define mesh for computation • Assign properties • Define boundary conditions (and initial conditions, if necessary) • Solve for the temperatures • Perform any desired post-processing
Overview (cont) • We’ll illustrate use of the program via an example -
Define Geometry • First set the grid to something convenient for drawing your 2-D geometry
Define Geometry • Then draw the outline of your object
Define Geometry • “Draw -> Outline…” tips • The crosshair cursor does not snap to the grid • Holding the “shift” key while drawing constrains the motion to straight lines • To make a corner you can click and continue to the next point
Define Mesh • When an outline is complete, the outline blinks, and the “Draw->Element Lines…” option is activated
Define Mesh • “Draw->Element Lines…” tips • Elements must be triangular • Element lines can only connect at nodes (you can’t join an element line to the middle of another element line!)
Define Mesh • Keep going…
Define Mesh • It can be tedious with a lot of nodes
Specify Properties • Click on one of the elements (NOT and edge or node) – the entire outline will begin blinking • Now go to “Specify->Material Properties” on the menu (or right click on the object)
Specify Properties • You can choose from a library of materials or select “not specified” and enter your own data
Apply Boundary Conditions • Either • Use the pointer to drag a box around a region of the boundary, or • Click on a segment of the boundary
Apply Boundary Conditions • The selected portion(s) of the boundary will blink • Choose “Specify->Boundary Conditions” or right click
Specify Boundary Conditions • Fill in the boundary condition information
Apply Boundary Conditions • At any time, “Run->Check” will tell the status of your model • After all boundaries have been assigned conditions, “Run->Calculate”
Post-Processing • “View->Temperatures” shows the computed nodal temperatures • “View->Temperature Contours” makes a color map of the solution • “View->Temperature Gradients” visualizes the heat flow directions • “View->Tabular Output” gives a table of the solution that can be cut/pasted